This is an Adkin (Advanced Kinetics) CO2 flowing gas laser - 50 W output.
It consists of the laser head, reflow chiller (not shown), control electronics
and power supply. The resonator has diffraction grating optics for specific
line selection and includes a piezoelectric positioning system for the optics
to allow for remote 'on the fly' selection of the laser line you wish. The
laser head is model MIRL-50-SL, the power supply is model LPS-50, and the
piezo controller is model PZT-2/3. Operates on 110/220VAC.

Since there are external line selecting optics, this laser uses Brewster
windows on the end of the tube - not that common with CO2 lasers due to losses
and large Brewster angle required for the window material (ZnSe?).